An area showing slow potentials is present at the perinodal region in humans. In patients with AVNRT, application of radiofrequency energy renders tachycardia noninducible through the preferential modification of the anterograde slow pathway. With present clinical methods, the exact origin and significance of these physiological potentials cannot be specified.

The present study provides evidence that the mechanism of successful AFI ablation targeting the IVC-TA isthmus is local bidirectional conduction block. This change can be used as a new and complementary electrophysiological end point for the procedure. AFI recurrences are associated with failure to achieve a permanent block.

The observations indicate that AF may be linked to "focal" mechanisms that can be treated by RF catheter ablation.

Catheter Ablation of AF. introduction: Catheter ablation of a case of incessant atrial fibriliation was attempted using linear right atriai lesions created by sequential applications of radiofrequency energy. Methods and Results:A 46-year-o!d patient had incessant episodes of atrial fibrillation. He had previously undergone successful radiofrequency catheter ablation of a common atrial flutter. Antiarrhythmic drugs including amiodarone and various drug combinations were ineffective. A 7-French specially designed 14-polar catheter with interelectrode distance of 3 mm was used to create linear lesions in the right atrium. Each electrode was 4 mm in length and able to transmit radiofrequency energy. Three linear lesions, two longitudinal and one transverse that connected the two longitudinal lesions, were created using 30 radiofrequency applications of 10 to 40 W. The final application interrupted an atrial fibrillation that had been persistent for 55 minutes. No sustained atrial fibrillation was inducible despite repeated pacing maneuvers. Tbere was no complication. In short-term follow-up of 3 months, the patient has been free of arrhythmias without antiarrhythmic medication.Conclusion: Successful catheter ablation of human atrial fibrillation is feasible using linear atrial lesions created by radiofrequency energy delivery. Furtber studies are mandatory to ascertain the efficacy and safety of this procedure, as well as to assess different catheter techniques.

Radiofrequency catheter ablation of atrial flutter can be performed with a high success rate and is safe. The highest success rate is achieved with radiofrequency energy applied in the isthmus between the inferior vena cava orifice and tricuspid valve.

Background-Catheter ablation of typical right atrial flutter is now widely performed. The best end point has been demonstrated to be bidirectional isthmus block. We investigated the use of irrigated-tip catheters in a small subset of patients who failed isthmus ablation with conventional radiofrequency (RF) ablation. Methods and Results-Of 170 patients referred for ablation of common atrial flutter, conventional ablation of the cavotricuspid isthmus with Ͼ21 applications failed to create a bidirectional block in 13 (7.6%). An irrigated-tip catheter ablation was performed on identified gaps in the ablation line according to a protocol found to be safe in animals: a moderate flow rate of 17 mL/min and temperature-controlled (target, 50°C) RF delivery with a power limit of 50 W. Bidirectional isthmus block was achieved in 12 patients by use of a mean delivered power of 40Ϯ6 W with a single application in 6 patients and 2 to 6 applications in the other 6. No side effects occurred during or after the procedure. Conclusions-Irrigated-tip catheter ablation is safe and effective for achieving cavotricuspid isthmus block when conventional RF energy has failed. (Circulation. 1998;98:835-838.)

No abstract

Transmural ablation lesions in the isthmus can be recognized during flutter by double potentials separated by an isoelectric interval. Postablation recurrent flutter is usually due to a single discrete recovered gap; this is represented by a single or a fractionated potential spanning the isoelectric interval of adjacent double potentials, which can be selectively targeted to minimize repeat ablation.